Shino is a subset of Mino pottery, which originated in the Gifu Prefecture of Japan. Mino wares are high-fired ceramics, which means that they were fired in a high-temperature kiln. ("High" of course being relative. I wouldn't want to hang out in a low-temperature kiln at 950 - 1100° C, but high-fired kilns must be able to melt the rocks that go into making glazes, at temperatures around 1300° C. High-fired wares are harder and more durable, less porous than low-fired earthenware.) There are several other kinds of Mino, namely yellow seto, black seto, and oribe, but shino is unique.
Potters in the region of Mino developed the "first uniquely Japanese tea ware"1 around the late fifteenth and early sixteenth century. Before then, tea ceremony instruments had been imported from China and Korea; growing demand (and growing alienation from China) made local production more necessary and economically supportable. Japanese wares tended to be less symmetrical and perfect, and more oriented toward the complete sensory experience of the vessel: the weight and texture as well as the way a thicker-walled chawan (tea bowl) would insulate the drinker's hands from the heat of the tea while still taking on a living warmth.
But this is just the pottery in general. Shino glaze is notable because it was the first white Japanese glaze. The potter's vocabulary back in the Momoyama Period had numerous blacks and reds and yellows, but the feldspar-based, thick and lustrous shino glaze captivated many followers of chadô (the way of tea). In particular, the brilliant green of the frothing tea was framed perfectly against the white and textured lip of the shino bowl.
Shino is a somewhat unpredictable glaze; while it is "stiff" and not prone to running and smoothing out in the kiln, it is prone to other effects like pitting, crazing, and carbon trapping. These imperfections were of course highly prized, and the patterning was sometimes enhanced by iron oxide brush marks over or under the glaze before firing. The reddish colored clay showing through translucent spots is known as hi-iro, or fire color. Tiny pits in the surface were called "citron skin" by tea people (think the texture of an orange peel) and prized highly. Shino is divided into subclasses according to the method and color of decoration: eshino (decorated with iron-oxide designs applied under glaze), muji Shino (plain white), aka-Shino (red Shino), beni Shino (red), nezumi Shino (gray or "mouse-colored").
This thick, somewhat globby glaze has had a resurgence of popularity among potters both in Japan and in the West. American potters experiment with recipes and techniques and have made in the name of shino a very diverse collection of work. While traditionally shino was used mostly on bowls, plates and cups (hardly ever vases) because the finish suited those settings and uses better, you'll find all kinds of large, abstract works in American shino ware these days. I'm not sure if they are designed for or conducive to the quiet, close, meditative experience of direct sensory engagement with the piece2, but some of them are quite nice to look at.
The Japanese Pottery Information Center at http://www.e-yakimono.net was indispensible in collecting this information.
1. according to Douglas M. Hooten, ceramicist, in his essay at http://www.dmh.net/raku98/RAKU.html.
2. I can't find it now, but i read one article that gave directions for interacting with a shino chawan at an exhibit. One is to pick them up - but not hold them up to the light, certainly not at arm's length. Instead, kneel by the exhibit table and cradle the chawan in your hands, feeling its balance as you lift it not more than a few centimeters above the surface. | 
